Last Updated: November 2025
So, you’ve determined that you need a rotary phase converter to power your three-phase equipment and machinery. The next step before purchasing is to determine which type of motor will best suit your application and environment.
At North America Phase Converter Co., one of the most common questions we hear from our customers relates to the different types of motors available and the differences between an open drip proof (ODP) motor and a totally enclosed fan cooled (TEFC) motor. The difference between ODP motors and TEFC motors relates to the motor enclosure and the type of debris and moisture it can withstand. The motor enclosure plays a crucial role in protecting the internal motor elements from contamination and damage.
Although we offer both options, it’s imperative to understand the differences between the two when making a purchasing decision to ensure the motor will run efficiently for your situation and have a long lifespan.
Open Drip-Proof (ODP) Motors
Key Characteristics
- Ventilation allows for enhanced cooling and airflow
- Indoor rated
- Smaller and less costly than TEFC motors
As implied by the name, ODP motors offer drip protection from overhead liquids. Open vents located on both sides of the motor allow external air to flow directly over the windings, effectively cooling the motor while it’s in use to prevent overheating. Because of this, ODP motors are usually cooler than TEFC motors when running. Our ODP idler motors (also known as Idler Generators) have an internal fan to keep the motor cool as well.
Because of the ventilation openings, airborne contaminants and dust can still get inside of the motor. To protect against these environmental factors, North America Phase Converter Co idler motors all include laminated windings and sealed bearings. Our ODP idler motors are completely safe to use in all indoor industrial environments.
Totally Enclosed Fan-Cooled (TEFC) Motors
Key Characteristics
- Cooling provided by an external fan
- Outdoor rated
- Reduced energy efficiency compared to ODP motors
TEFC motors have a closed-off enclosure chamber, meaning there are no vent openings on the side of the motor. Instead, an external fan blows air over the enclosure for cooling. The closed-off exterior effectively protects the motor from external contaminants, including dust, dirt, moisture, and various weather-related disturbances.
The most common reason for choosing a TEFC motor is its ability to handle being in outdoor or damp/wet locations, preventing liquid or solid contaminants in these environments from damaging the internal motor contents.
While it’s tempting to choose an ODP motor due to the lower cost, if your rotary phase converter is going to be outdoors, the initial upfront investment in a TEFC motor will help to minimize potential maintenance costs down the line. This is because the TEFC motor is better suited for rough outdoor conditions.
Common Applications for Each Type
For most applications and equipment, an ODP motor is the right choice, and a TEFC motor is not necessary. ODP motors are better suited for clean and dry indoor environments where the risk of particle exposure is limited. Thanks to their superior cooling capabilities, ODP motors are less likely to overheat in these conditions, making them a dependable choice for most of the applications we see at NAPCco.
ODP Applications
- Indoor manufacturing
- Food service equipment (ovens, dough mixers, etc.)
- HVAC units and systems
- Metalworking
- Woodworking
- Welding
- Automotive
TEFC Applications
- All outdoor settings
- Wet and/or damp locations
- Food service washdown areas
Energy Efficiency
Energy efficiency varies slightly between the two motor types. An ODP motor ventilation system helps with heat dissipation, making it more energy efficient in indoor environments where exposure to contaminants and moisture is minimal. Efficient cooling means less energy is lost to heat, and the motor can maintain optimal performance. On the other hand, since TEFC motors use an external fan for cooling, heat dissipates more slowly. This makes TEFC motors slightly less energy efficient.
Ultimately, if your application is in a dry, indoor environment, ODP motors offer a slightly more energy-efficient solution. However, in outdoor settings where protection from contaminants and moisture is critical, the slight trade-off in energy efficiency with TEFC motors is outweighed by the increased reliability and protection of internal parts. Choosing the right motor enclosure ensures both optimal performance and long-term savings for your equipment.
Maintenance for Reliable Performance
Like any tool or piece of machinery, it’s important to inspect the motor and provide maintenance accordingly. This will help increase the longevity of your rotary phase converter and ensure peak performance.
The buildup of contaminants on the inside or outside of the motor can act as insulation, potentially causing overheating. For ODP Motors, make sure vents are clear and clean, cleaning off any debris buildup from time to time. Users should also follow all maintenance and cleaning recommendations specified in their product manual.
Choosing your Motor
Overall, both motor types are equally effective at converting single-phase power into three-phase power. However, the lifetime of the motor can be extended by choosing the right one for your setup. Considering the factors mentioned above can help reduce potential downtime and maintenance needed in the long run, ensuring your rotary phase converter works for years to come.
When it comes to purchasing on our website, each Phase Converter automatically comes with an ODP motor as the standard option. To purchase a TEFC motor for your rotary phase converter, scroll to the “Available Options” section and click on the box next to “Idler/Generator: TEFC (Outdoor)”.
If you are unsure what motor is best for your needs, our dedicated team of technicians is available to help you determine the most effective solution. Please contact us for more information.
